Atomistic modeling of the interaction of cladding elements (Fe, Ni, Cr) with U–Zr fuel

Atomistic simulations of U–Zr fuel and its interaction with Fe, Ni, and Cr using the BFS method for alloys are presented. Results for the γU–βZr solid solution are discussed, including the behavior of the lattice parameter and coefficient of thermal expansion as a function of concentration and temperature. Output from these calculations is used to study the surface structure of γU–βZr for different crystallographic orientations, determining the concentration profiles, surface energy, and segregation behavior. The analysis is completed with simulations of the deposition of Fe, Ni and Cr on U–Zr substrates with varying Zr concentration. All results are discussed and interpreted by means of the concepts of strain and chemical energy underlying the BFS method, thus obtaining a simple explanation for the observed Zr segregation and its influence in allowing for cladding elements diffusion into the U–Zr fuel.